Finally this morning. We're back in Baghdad, where the situation is truly heartbreaking. Knowing the sacrifice that Americans made here and remembering the decision to invade this country in the first place. The military did not choose this war. That is always the decision made by civilians. But they took on the task they were given, losing nearly 4500 men and women on the way. Hoping that someday, it would be worth it. It is perhaps this image that is most iconic to Americans. That day shortly after the invasion when Iraqis tore down that statue of saddam hussein. Today, this sight is just a weed-covered traffic circle. Known only for the numerous bombs planted nearby in recent months. For me, it is the northern city of mosul that leaves some of the most powerful memories. Walking through the market as U.S. Troops gained control of the volatile city. In 2005, an historic election. Long lines of voters risking death to cast ballots. Iraqi forces celebrating. A good friend of mine. Reporter: And the U.S. General in charge so proud of what the Iraqi people accomplished. There are some great people. Some very brave people. And the opportunity to see them stand tall on their own was very, very rewarding. It was certainly in my life the most important day that I have personally been involved in. And a proud day for all Americans and certainly for all Iraqis. Reporter: Today, it is impossibly dangerous to get anywhere near mosul. It quickly fell to Isis militants after the security forces, of whom general hamm was so proud, dropped their weapons and ran. And Al anbar province, where the corpses of Americans working for blackwater were hung from a bridge, where the risk of snipers was so fierce we had to run from building to building to stand a chance. And where Americans waged a major assault to push out the militants. Our goal is not the take the town or seize the town. Our goal is to return the town of fallujah back to their people. Reporter: They did at great cost. Today, fallujah, too, has fallen to the jihadists. And then, there is Baghdad. The city that, for so many years, the U.S. Military feared would fall. A decade ago, general peter Chiarelli was determined to make life better for the people here. Better electricity. A Riverside park. Three weeks ago, this was all rubble, garbage. And it's going to be beautiful when it's done. Reporter: This is that park today. It is beautiful. A tiny oasis of hope for families amid so much that has been shattered. Of course, there is no guarantee that Baghdad will not fall. The people here are determined to hold the city, no matter what the cost. After this terrible week in Iraq, we end with welcome news from Afghanistan. No deaths of U.S. Service members reported this week. That's all for us today. Thanks for sharing part of your Sunday with us. Check out "World news" with David Muir tonight. So long from Baghdad.

This transcript has been automatically generated and may not be 100% accurate.

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